The invention relates to a method of producing an acid-resistant and electrically conductive building material covering on a mechanically stable substrate, for instance on a floor or a wall.
A method of the type referred to above is disclosed in, for instance, the worksheet, p 30, from the Arbeitsgemeinschaft Industriebau e.V. (AGI) dated December 1994, which contains instructions for producing electrically conductive floor coverings. Such floor coverings are required with an acid-resistant construction where special requirements are present relating to detonation risks as a consequence of electrostatic charges, for instance in regions at risk of explosion. In order to produce such floor coverings, a sealing layer (sealing sheet or liquid film) is firstly applied to a substrate. Tiles or plates are laid on this sealing layer in a bedding material. After setting or bonding of the bedding material, the joints between the tiles or plates are filled with a grouting material. The bedding material must be electrically conductive. In order to produce contact with an earth connection, conductive copper strips are embedded in the bedding material beneath the tiles or plates. The floor coverings can be produced with continuously conductive plates, with tiles with a conductive glaze or with non-conductive plates. If continuously conductive plates are used, the grouting material can also comprise a non-electrically conductive cement or mortar. If tiles with a conductive glaze are used, conductive cement or mortar must be used both for the bedding material and for the grouting material.
The same applies when using non-conductive plates; in this case the plates should additionally not exceed a maximum size and the butt joints must be flush with the surface.
Synthetic resin cements, for example, are used as electrically conductive bedding and grouting materials, the specific resistance of which is reduced by additives, such as granular coke, graphite, carbon fibres and soot, to the extent that they have the conductivity necessary for grounding electrical charges. Hydraulically setting mortars are also used which are made to be electrically conductive by mixing in graphite or soot. The above specification defines an object as conductive if its specific resistance less than 10xcexa9*m. As well as the addition of electrically conductive particles based on carbon, as an alternative the addition of metallic powders, metallic fibres or metallised glass, ceramic and plastic bodies is recommended.
Of disadvantage with the mixtures made conductive with carbon particles is, above all, their dark coloration, which limits the breadth of variation of the design possibilities, above all in the joint region. The addition of metal particles, on the other hand, can result in an impairment of the acid resistance.